Air-Ground Study of Tectonics at the Boundary Between the Eastern Ross Embayment and Western Marie Byrd Land, Antarctica: Basement Geology and Structure

摘要该奖项支持一个合作项目，该项目结合了空中和地面地质-地球物理调查，以了解罗斯海裂谷和玛丽伯德地（MBL）火山省之间边界的构造和地质发展。该项目将确定该地区的新生代构造历史，以及局部出口冰川流的新近纪构造是在罗斯湾东部边缘的新生代裂谷背景下发育的，还是在MBL的火山省内发育的。罗斯湾与西海带交界的地质构造可能是：1)新生代罗斯海裂谷东肩伸展作用的结果；2) MBL西部新近系地幔柱活动相关的隆升和地壳伸展；或者两者的结合。断裂和火山作用、山脉隆升和冰川下切活动活跃于MBL西部地区，在该地区，通常由东向西流动的出入口冰川切割古生代和中生代基岩，冰川消融的峰顶表明以前的南北冰川流动方向。这项研究需要使用SOAR（航空地球物理研究支持办公室，一个由极地项目办公室支持的设施，它利用高精度差分GPS来支持激光高度计、破冰雷达、牵引质子磁力计和贝尔BGM-3重力仪）收集数据。本次调查需要的数据面积为3.7万平方公里，线间距为5.3公里，线间距为15.6公里，网格间距为10.6 × 10.6公里，数据面积为8.6万平方公里。将获取该地区几个关键特征的数据，其中包括罗斯海裂谷的东部边缘、冰流OEO上方、爱德华七世半岛高原向福特山脉的过渡、从先前对福斯迪克变质杂岩的侦察测绘中已知的重力高压向东的延续、以及其他研究人员在福特山脉北部东南部探测到的高振幅磁异常（火山中心？）的范围。SOAR产品将包括对研究南极西部冰盖（WAIS）的驱动应力、冰川流动和物质平衡有用的冰川学数据。地面项目以福特山脉南部为中心。地质野外测绘将集中在小尺度脆性结构上进行区域运动学解释，集中在冰川表面和沉积物上，集中在可测定年代的火山岩上进行地质年代学控制。断层和节理组的相对意义、它们之间的时间关系以及它们形成的可能背景也将被确定。将确定侵蚀面和冰碛的暴露年龄。对势场数据的解释将借助于对磁性和密度的地面采样以及地面重力测量。定向样品将用于古地磁研究。机载和地面联合调查将获得描述罗斯海湾东部边界露头和冰覆盖区域的地质和构造的基本数据，并可用于区分与罗斯海裂谷有关的构造活动，包括MBL穹窿和火山省周边的隆起和断裂。利用航空地球物理数据推断出露头地质和构造，从而推断出位于WAIS下方的地质。对MBL西部新近系构造的新认识将有助于建立一个完整的新生代罗斯裂谷模型，并有助于了解MBL地幔柱活动的程度。两者对于确定新近纪构造对冰流和WAIS的影响具有重要意义。

OPP 9615281 Luyendyk OPP 9615282 Siddoway Abstract This award supports a collaborative project that combines air and ground geological-geophysical investigations to understand the tectonic and geological development of the boundary between the Ross Sea Rift and the Marie Byrd Land (MBL) volcanic province. The project will determine the Cenozoic tectonic history of the region and whether Neogene structures that localized outlet glacier flow developed within the context of Cenozoic rifting on the eastern Ross Embayment margin, or within the volcanic province in MBL. The geological structure at the boundary between the Ross Embayment and western MBL may be a result of: 1) Cenozoic extension on the eastern shoulder of the Ross Sea rift; 2) uplift and crustal extension related to Neogene mantle plume activity in western MBL; or a combination of the two. Faulting and volcanism, mountain uplift, and glacier downcutting appear to now be active in western MBL, where generally East-to-West-flowing outlet glaciers incise Paleozoic and Mesozoic bedrock, and deglaciated summits indicate a previous North-South glacial flow direction. This study requires data collection using SOAR (Support Office for Aerogeophysical Research, a facility supported by Office of Polar Programs which utilizes high precision differential GPS to support a laser altimeter, ice-penetrating radar, a towed proton magnetometer, and a Bell BGM-3 gravimeter). This survey requires data for 37,000 square kilometers using 5.3 kilometer line spacing with 15.6 kilometer tie lines, and 86,000 square kilometers using a grid of 10.6 by 10.6 kilometer spacing. Data will be acquired over several key features in the region including, among other, the eastern edge of the Ross Sea rift, over ice stream OEO, the transition from the Edward VII Peninsula plateau to the Ford Ranges, the continuation to the east of a gravity high known from previous reconnaissance mapping over the Fosdick Metamorphic Complex, an d the extent of the high-amplitude magnetic anomalies (volcanic centers?) detected southeast of the northern Ford Ranges by other investigators. SOAR products will include glaciology data useful for studying driving stresses, glacial flow and mass balance in the West Antarctic Ice Sheet (WAIS). The ground program is centered on the southern Ford Ranges. Geologic field mapping will focus on small scale brittle structures for regional kinematic interpretation, on glaciated surfaces and deposits, and on datable volcanic rocks for geochronologic control. The relative significance of fault and joint sets, the timing relationships between them, and the probable context of their formation will also be determined. Exposure ages will be determined for erosion surfaces and moraines. Interpretation of potential field data will be aided by on ground sampling for magnetic properties and density as well as ground based gravity measurements. Oriented samples will be taken for paleomagnetic studies. Combined airborne and ground investigations will obtain basic data for describing the geology and structure at the eastern boundary of the Ross Embayment both in outcrop and ice covered areas, and may be used to distinguish between Ross Sea rift- related structural activity from uplift and faulting on the perimeter of the MBL dome and volcanic province. Outcrop geology and structure will be extrapolated with the aerogeophysical data to infer the geology that resides beneath the WAIS. The new knowledge of Neogene tectonics in western MBL will contribute to a comprehensive model for the Cenozoic Ross rift and to understanding of the extent of plume activity in MBL. Both are important for determining the influence of Neogene tectonics on the ice streams and WAIS.